FRP lining construction for underground tanks for storing fuels such as ethanol-mixed gasoline

Abstract

To provide a buried tank capable of reliably preventing corrosion, pitting, fuel leakage, etc. [Solution] A buried tank 1 for storing fuels such as ethanol-blended gasoline, biodiesel fuel, organic solvents, etc., has an opening, and a cleaning process is performed by entering through the opening to clean the inside of the buried tank, and a repair and renovation process is performed to repair and renovate the inside of the buried tank after the cleaning process.The buried tank is equipped with a first FRP sheet of a specified width on the inner surface of the buried tank, and a second FRP sheet of a specified width formed on the first FRP sheet.

Description

[Technical field]

[0001] This invention relates to the construction of FRP linings for underground tanks that store mixed fuels such as ethanol-mixed gasoline and biodiesel, and fuels such as organic solvents. [Background technology]

[0002] Nowadays, underground oil storage tanks are widely used at gas stations, etc. Conventionally, fuels such as gasoline and diesel were stored in such underground oil storage tanks, but nowadays, various fuels such as mixed fuels such as ethanol-mixed gasoline and biodiesel, and organic solvents such as ethanol, methyl ester, and ketone are used, and it is necessary to store such fuels in underground storage tanks as well.

[0003] For example, ethanol-blended gasoline is a fuel made by mixing gasoline and ethanol in a certain ratio, while biodiesel fuel is a renewable fuel made from biological resources such as corn and other plants.

[0004] On the other hand, underground storage tanks may deteriorate over time through use, and may become corroded or pitted, and if fuel leaks occur, problems such as soil contamination may occur. Therefore, repairs to underground storage tanks are necessary. Patent Document 1 proposes a fuel tank repair method that prevents the leakage of flammable fuel from existing fuel tanks without replacing the deteriorated existing fuel tanks with new fuel tanks. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2002-211685 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, as mentioned above, underground tanks storing various fuels such as the latest ethanol-mixed gasoline, biodiesel fuel, and organic solvents require repairs that are different from those used for conventional underground storage tanks. The reason for this is that, for example, in the case of mixed gasoline, as mentioned above, mixed gasoline is a fuel made by mixing gasoline and ethanol in a certain ratio, and is prone to deterioration and cannot be repaired using conventional repair methods. In addition, in the case of biofuels, waste-based biofuels are often used, and the corrosion of the inner surface of the tank is severe, making it impossible to repair using conventional repair methods.

[0007] In addition, when lining the inside of buried tanks using FRP (fiber-reinforced composite material), the effectiveness of preventing corrosion and pitting varies significantly depending on the construction method. [Means for solving the problem]

[0008] According to the present invention, the above-mentioned object can be achieved by providing an FRP lining construction for an underground tank for storing fuel, which comprises the following steps: an opening process for forming an opening in a buried tank for storing fuel such as ethanol-blended gasoline, biodiesel fuel, or organic solvents; a cleaning process for entering through this opening and cleaning the inside of the buried tank; a repair and renovation process for repairing and renovating the inside of the buried tank after the cleaning process; a first attachment process for attaching a first FRP sheet of a predetermined width to the inside of the buried tank after the repair and renovation process; and a second attachment process for attaching a second FRP sheet onto the first FRP sheet.

[0009] Also, the above-mentioned thickness can be achieved by providing a method for repairing a tank using an FRP sheet having a thickness greater than that of the second FRP sheet.

[0010] Also, this can be achieved by providing a method for repairing a tank using FRP, in which the first FRP sheet is attached by overlapping an adjacent FRP sheet with a predetermined width, and the second FRP sheet is attached onto the first FRP sheet so that the center of the second FRP sheet is positioned in the overlapping portion. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a cross-sectional view of a buried tank for explaining the present embodiment. [Diagram 2] A cross-sectional view of the buried tank after the tank has been opened. [Diagram 3] FIG. 1 is a diagram illustrating an FRP lining construction process inside a tank. [Figure 4] FIG. 1 is a diagram illustrating an FRP lining construction process inside a tank. [Diagram 5] 10A to 10C are diagrams illustrating another lining construction process of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram for explaining the configuration of a buried tank to which the lining construction of this embodiment is applied. In the figure, 1 is a buried tank buried underground, and buried tank 1 can store ethanol mixed gasoline, biodiesel fuel, or organic solvents such as ethanol, methyl ester, and ketone. 2 is a supply pipe for supplying the mixed gasoline to buried tank 1, and 3 is a suction pipe used to suck up the stored mixed gasoline.

[0013] The buried tank 1 is provided with a vent pipe 4 for ventilating the inside of the tank, and a metering port (not shown) for metering mixed gasoline, etc. The buried tank 1 is buried at a prescribed depth from the ground surface, and concrete 5 is laid on top of the buried tank 1. The supply pipe 2 is provided with a valve 6, and the suction pipe 3 is provided with a valve 7. When repairing or renovating the buried tank 1, the valves 6 and 7 are closed.

[0014] In the buried tank 1 having the above-mentioned configuration, the FRP lining process inside the tank, including the opening process of the buried tank 1, will be described. First, the combustible gas inside the buried tank 1 is measured. This process checks the internal gas concentration and the presence or absence of fuel leakage using a measuring device (not shown). If there is any abnormality in the gas concentration or fuel leakage, these are immediately removed to make the buried tank safe.

[0015] Next, when the safety of the buried tank 1 has been confirmed by the above process, the mixed gasoline, biomass fuel, or organic solvent inside the buried tank 1 is removed. This work involves disconnecting piping such as the supply pipe 2 and suction pipe 3, removing the fuel gauge, inserting a suction hose, and removing the mixed gasoline, etc. from the tank using, for example, an air-driven pump or a pressure-resistant explosion-proof pump.

[0016] Next, water is poured into the buried tank 1 and oil absorbent material is sprayed. For example, after removing the mixed gasoline from the tank as described above, water is poured in through the supply pipe 2 to fill the buried tank 1. The amount of water is about half the tank capacity, and after filling, the water reaches near the center of the buried tank 1. After the water is filled, an organic oil absorbent is spread and the floating oil is absorbed by the organic oil absorbent. The water from which the oil has been separated is discharged into a drain via an oil-water separator (not shown).

[0017] Next, a water pressure test is performed on the buried tank 1 and each of the pipes 2 and 3. In this test, after the floating oil has been removed, the buried tank 1 is filled with water, and the water pressure is increased to, for example, 0.7 kg / m, and a water pressure test is performed on the buried tank 1, supply pipe 2, and suction pipe 3 to check for the presence or absence of water leakage.

[0018] Next, the buried tank 1 is disconnected from each of the pipes 2 and 3. In other words, all of the pipes connected to the buried tank 1 are disconnected.

[0019] Next, the opening to be formed in the buried tank 1 is marked out, and a temporary fence is installed. The position of the opening to be formed in the buried tank 1 is determined based on the structural drawing of the buried tank 1. After the position of the opening is marked out, the periphery is covered with a temporary fire fence.

[0020] Next, the concrete 5 formed on the buried tank 1 is removed, and excavation work is carried out. Here, the position of the concrete 5 is particularly indicated by 5' in Fig. 1. In this process, the concrete 5' is cut by a concrete excavator along the marked line, and after cutting, the concrete 5' is broken up by a concrete breaker, and the soil 8 is excavated until the buried tank 1 appears.

[0021] Next, the anti-corrosion coating is removed. That is, the anti-corrosion coating applied to the buried tank 1 is removed in accordance with the opening of the tank.

[0022] Next, the buried tank 1 is opened. This opening is done with an air cutter, and when the opening work is completed, the water seal bath is removed. Figure 2 shows the buried tank 1 and its surroundings after the above-mentioned series of operations. The reference number 9 in the figure indicates the opening.

[0023] Once the opening work is completed as described above, the tank is cleaned. In tank cleaning work, the water in the buried tank 1 is pumped out using an air-driven pump or a pressure-resistant explosion-proof pump, and discharged through an oil-water separator. After the water is drained, an organic oil absorbent is spread on the sludge inside the buried tank 1, and then a 6% emulsified solution, for example, is added to the surface to extremely reduce the generation of volatile gases, and the sludge is disposed of together with the cleaning wastewater inside the buried tank 1.

[0024] When the cleaning work inside the buried tank 1 is completed as described above, the inside of the buried tank 1 is inspected. First, the inside of the buried tank 1 is visually inspected. This visual inspection is performed by sandblasting or buffing with a wire brush over the entire inside of the buried tank 1, exposing the bare surface of the tank body.

[0025] Next, a visual inspection is performed over the entire interior of the buried tank 1 to check the location and number of corrosion, scratches, jig marks, etc. Here, the hole contact measurement is performed to check the depth, location, number, etc. of the hole contact parts found by visual inspection, etc. In addition, the plate thickness measurement is performed by using an ultrasonic thickness measuring device to measure the plate thickness of the entire interior, including the shell and head plate.

[0026] Penetrant testing involves inspecting the weld lines throughout the tank interior, the nozzle neck welds, and visually inspecting any damaged areas such as cracks. Next, the tank is repaired and renovated. If the inspection and testing of the inside of the tank indicates that some kind of repair is required, a specific renovation plan is made based on a comprehensive judgment including the selection of repair materials, renovation method, maintenance measures, and construction period, depending on the situation, as follows: In other words, a renovation plan is made using plate welding, overlay welding, anti-corrosion coating, or other effective methods, and is then implemented.

[0027] Next, the FRP lining is applied to the inside of the tank. The lining is applied to the inside of the tank by first sandblasting or buffing with a wire brush to prepare the base, and then applying a primer coat. After applying the primer coat, a specified number of layers of FRP prepreg sheets are stacked and hardened under ultraviolet fluorescent lamps.

[0028] 3 and 4 are cross-sectional views of a buried tank 1 specifically illustrating the lining construction process inside the tank. The buried tank 1 is made of steel plates, and has been repaired as described above. An FRP prepreg sheet is attached to the inside of the buried tank 1. Here, FRP (fiber reinforced composite material) is a composite material in which, for example, plastic, metal, rubber, etc. are reinforced with high-strength fibers, and glass fiber composite material, carbon fiber composite material, etc. can be used.

[0029] A specific method for attaching FRP will be described below. First, after applying a primer coat to the base as described above, the prepreg sheet 11 is attached starting from a predetermined position on the inner surface of the buried tank 1. That is, as shown in Fig. 3, starting from position 10a inside the buried tank 1 showing the cross-sectional shape, the FRP (prepreg sheet) 11 is attached counterclockwise for 240° along the inner surface of the tank 1, and is attached to position 10b.

[0030] Also, adhesive is applied to the FRP (prepreg sheet) 11 in advance, and the FRP (plastic sheet) 11 is peeled off before use, and when it is attached to the inner surface of the buried tank 1, it is attached so that no gas phase is generated between the inner surface of the buried tank 10 and the FRP (prepreg sheet) 11. Also, the above-mentioned attachment work of the FRP (prepreg sheet) 11 is performed sequentially from one end to the other end in the longitudinal direction of the buried tank 1. In this way, the FRP (prepreg sheet) 11 is attached within a range of 240° to the middle and lower layers of the buried tank 1.

[0031] In this way, once the attachment of the FRP (prepreg sheet) 11 to the middle and lower layers of the buried tank 1 is completed, the attachment process for the upper layer of the buried tank 1 is performed next. Fig. 4 is a diagram for explaining the attachment process for the upper layer of the buried tank 1. As shown in the figure, the FRP (prepreg sheet) 11 is attached to the area except between positions 10a and 10b by the above-mentioned process. Therefore, in order to attach the FRP (prepreg sheet) 11 to this interval, the attachment start position of the FRP (prepreg sheet) 11 is set to 10b, and the FRP (prepreg sheet) 11 is attached up to the attachment end position 10a.

[0032] That is, the FRP (prepreg sheet) 11 is attached in a counterclockwise direction, and the FRP (prepreg sheet) 11 is attached to the upper layer of the buried tank 1 within a range of 120°.

[0033] By carrying out the bonding process as described above, the FRP (prepreg sheet) 11 is bonded to the entire inner circumferential surface of the buried tank 1. Finally, the FRP (prepreg sheet) 11 is irradiated with ultraviolet light to harden the FRP (prepreg sheet) 11.

[0034] After that, work such as installing manholes will be carried out, and after the installation of the inspection hatch is completed, all openings of buried tank 1 will be sealed, an airtight test will be conducted, and restoration work will be carried out. As described above, according to this embodiment, the buried tank 1 is repaired and renovated by entering the tank through the opening 9 and carrying out the FRP lining construction process shown in Figures 3 and 4, thereby making it possible to reliably repair corrosion, pitting, oil leaks, etc. of the buried tank.

[0035] In addition, after repair and renovation according to this embodiment, the buried tank 1 will deteriorate over time, but the progression of this deterioration will be slowed down by the construction of the FRP, making it possible to use the buried tank 1 for a long period of time.

[0036] In the description of this example, the FRP 11 is applied to the middle and lower layers at 240°, but it does not necessarily have to be applied to 240°. Also, the upper layer may be applied to the remaining range.

[0037] In addition, in the above embodiment, the lining construction using FRP was described, but it is also possible to form a layer of FRP inside the buried tank by applying FRP to the inner wall of the tank using a brush or the like, or by spraying FRP onto the inner wall of the tank.

[0038] Here, the process of applying FRP to the inner wall of a tank using a brush or the like refers to a process in which an operator holds a roll brush or bristle brush and applies FRP to the inner wall of the tank, while the process of spraying FRP onto the inner wall of a tank refers to a process in which an operator holds a spray gun pressurized by a compressor and sprays liquid FRP onto the inner wall of the tank.

[0039] By carrying out the treatment in this manner, an FRP layer can be formed on the inner wall of the buried tank 1, and the buried tank can be reliably repaired or renovated.

[0040] Next, another embodiment of the present invention will be described. 5 is a diagram specifically illustrating the lining construction process of another embodiment, and is a cross-sectional view of a buried tank 20. The buried tank 20 is made of steel plates, and has been repaired as described above. An FRP prepreg sheet is attached to the inside of the buried tank 20.

[0041] Here, FRP (fiber reinforced composite material) is a composite material in which, for example, plastic, metal, rubber, etc. are reinforced with high-strength fibers, and glass fiber composite material (GFRP (Glass fiber reinforced plastics)), carbon fiber composite material, etc. can be used.

[0042] A specific method for attaching the FRP will be described below. First, after applying a primer coat to the base as described above, the FRP sheet 21 is attached starting from a predetermined position on the inner surface of the buried tank 20. That is, as shown in Fig. 5, the FRP sheet 21 is attached along the inner surface of the tank 20 starting from position 30 inside the buried tank 20.

[0043] Here, the FRP sheet 21 has a predetermined length, for example, a sheet having a thickness of 1.3 mm and a width of 50 cm is used. Also, the FRP sheet 11 is coated with adhesive in advance, and is used after removing the protective film.

[0044] First, for example, FRP sheet 21-1 is attached starting from position 30 inside buried tank 20. At this time, the attachment is performed so that no gas phase is generated between the inner surface of buried tank 20 and FRP sheet 21-1. Next, starting from position 21-1'', for example, 5 cm inward from end 21-1' of FRP sheet 21-1, the next FRP sheet 21-2 is attached so that it partially overlaps FRP sheet 21-1. In other words, the next FRP sheet 21-2 is attached 5 cm inward from end 21-1' of FRP sheet 21-1, overlapping it.

[0045] Next, as described above, FRP sheet 21-3 is attached starting from position 21-2'' 5 cm inward from end 21-2' of FRP sheet 21-2 so as to overlap partially on FRP sheet 21-2. In other words, the next FRP sheet 11-3 is attached 5 cm inward from end 21-2' of FRP sheet 21-2, overlapping it.

[0046] Similarly, FRP sheets having a thickness of 1.3 mm are successively attached in a counterclockwise direction, and when the first position 30 is reached, FRP sheets 21-1 to 21-n are attached after going around the buried tank 20.

[0047] Next, a second FRP sheet 22 having a thickness of 0.8 mm is attached onto the FRP sheets 21-1 to 21-n. This second FRP sheet 22 also has a width of 50 cm, similar to the first FRP sheet 21, and is pre-coated with an adhesive.

[0048] Here, the FRP sheet 22 is attached as follows. That is, the FRP sheet 22-1 is attached so as to cover from the center 21-1c of the FRP sheet 21-1 to the center 21-2c of the adjacent FRP sheet 21-2. Therefore, the FRP sheet 22-1 is attached so that the overlapping portion of the FRP sheets 21-1 and 21-2 is at the center. Note that, in this case as well, the FRP sheet 22-1 is attached so as not to generate a gas phase between the FRP sheets 21-1 and 21-2.

[0049] Next, FRP sheet 22-2 is attached so as to cover the area from center 21-2c of FRP sheet 21-2 to center 21-3c of the adjacent FRP sheet 21-3. Therefore, in this case as well, FRP sheet 22-2 is attached so that the overlapping portion of FRP sheets 21-2 and 21-3 becomes the center.

[0050] Similarly, FRP sheets 22-3, 22-4, ... 22-n, each having a thickness of 0.8 mm, are successively adhered onto FRP sheets 21-3, 21-4, ... 21-n, until the initial position 30 is reached, after which FRP sheets 22-1 to 22-n are layered and adhered onto FRP sheets 21-1 to 21-n after going around the buried tank 20.

[0051] In this way, by covering the FRP sheets 21-1 to 21-n attached to the inner surface of the buried tank 20 and attaching FRP sheets 22-1 to 22-n in a doubly manner, it is possible to reliably protect the buried tank 20 from corrosion and pitting. In particular, in the tank repair method using FRP of this example, the FRP sheets 22-1 to 22-n are attached so that their centers are positioned in the overlapping portions of the FRP sheets 21-1 to 21-n, so that it is possible to propose a tank repair method using FRP that can better prevent fuel leakage.

[0052] By carrying out the bonding process as described above, the FRP sheets 21 and 22 are bonded to the entire inner circumferential surface of the buried tank 20 in a double layer, and finally, the FRP sheets 21 and 22 are hardened by irradiation with an ultraviolet fluorescent lamp.

[0053] Thereafter, work such as installing manholes is carried out, and after installation of the inspection hatch is completed, all openings of the buried tank 20 are sealed, an airtight test is performed, and then restoration work is carried out.

[0054] As described above, according to this embodiment, the FRP lining can be more reliably applied, and corrosion, pitting, fuel leakage, and the like of the buried tank 20 can be reliably prevented. In the description of this example, the 1.3 mm thick FRP sheets 21-1 to 21-n are first attached, and then the 0.8 mm thick FRP sheets 22-1 to 22-n are attached on top of them. However, the 0.8 mm thick FRP sheets 21-1 to 21-n may be attached first, and then the 1.3 mm thick FRP sheets 22-1 to 22-n may be attached on top of them. [Explanation of symbols]

[0055] 1. Buried tank 2. Oil supply pipe 3...Suction tube 4. Ventilation pipe 5, 5′ Concrete 6, 7 Valves 10...Start position 11, 11-1 to 11-n: FRP sheet 11-1′~11-n′·End part 11-1″~11-n″·Position 11-1c~11-nc...center position 12, 12-1 to 12-n FRP sheet 20 Buried tank 21, 21-1, 21-2, ...FRP sheet 22, 22-1, 22-2, ...FRP sheet 21-1′, 21-2′ Ends 30...position

Claims

1. An opening process for forming an opening in a buried tank for storing fuel such as ethanol-blended gasoline, biodiesel fuel, or organic solvent; a cleaning process for entering through the opening and cleaning the inside of the buried tank; A repair and renovation process for repairing and renovating the inside of the buried tank after the cleaning process; a process of attaching a first FRP sheet of a predetermined width to the inside of the buried tank after the repair and renovation process; A process of adhering a second FRP sheet onto the first FRP sheet; A method for repairing a tank using FRP, comprising the steps of:

2. 2. The method for repairing a tank using FRP according to claim 1, wherein the thickness of the first FRP sheet is greater than the thickness of the second FRP sheet.

3. 3. The method for repairing a tank using FRP as described in claim 1 or 2, characterized in that the first FRP sheet is attached by overlapping it with an adjacent FRP sheet with a predetermined width, and the second FRP sheet is attached onto the first FRP sheet so that the center of the second FRP sheet is located in the overlapping portion.

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